Capacitive coupling assembly



y May 27 1952 EJM. osfrLUND CAPACITIVE couPLING ASSEMBLY Filed May 25, 1945 hww-lwll NNW INVENTOR. fVf/PT M STLU/VD BY /TTIP/VEY Patented May 27, 1952 CAPACITIVE GOUPLING ASSEMBLY Evert M. Ostlund, Montclair, N. J., assignor to Federal Telephone and Radio Corporation, New York, N. Y., a corporation of Delaware Application May 23, 1945, Serial No. 595,300

9 Claims.

The present invention relates to a capacitive"v coupling assembly, and particularly to one adapted to serve as a by-pass condenser between a hollow conductor and one or more transmission lines extending within said conductor.

In certain applications where one or more conductors extend within a hollow conductor, it is desired to capacitively couple the inner conductors to the hollow conductor. A typical example of such application is foundkin certain coaxialy line oscillators in which transmission lines apply direct current voltages from a power pack to the cathode terminals of the vacuum tube in said oscillators, while a hollow conductor, surrounding said transmission lines and forming the inner conductor of a coaxial line, is required to carry the radio frequency voltages appearing at said cathode terminals. To keep the radio frequency voltages out of the power supply and in the coaxial line, a by-pass condenser arrangement, or capacitive coupling assembly, is provided adjacent the cathode terminal capacitively coupling each of the transmission lines which are connected with the cathode terminal to the hollow conductor. A similar by-pass condenser arrangement is provided towards the opposite end of the hollow conductor so that the hollow conductor is capacitively short-circuited at both ends to the transmission lines to thereby prevent the hollow conductor from forming resonant sections with the transmission lines and thus preventing any externally originated radio frequency current from entering the coaxial line through such means.

An object of the present invention is the provision of an improved capacitive coupling assembly.

One of the features of the assembly embodying my invention is that the dielectric of the by-pass condenser between the transmis-sion lines and the hollow conductor surrounding said lines is continuous and is not perforated for mounting purposes. Another advantage of the assembly embodying my invention is that the leakage paths around the edges are long. A feature of this assembly is that it may be readily mounted within the hollow conductor, and likewise readily removed. Another important feature of the assembly embodying my invention is the shortness of the radio frequency paths between the hollow conductor and the inner conductors to which it is capacitively coupled by said assembly. The short radio frequency paths provided by this assembly have low inductive reactance.

Other and further objects, advantages and features of the present invention will become apparent and the invention will be best understood from the following description of an embodiment thereof, reference being had to the drawing, in which:

Fig. l is an elevational view, partly broken away, of a coaxial line oscillator including an embodiment of the capacitive coupling assembly of my invention;

Fig. 2 is an end view of the assembly illustrated in Fig. 2; and

Fig. 3 is a sectional view taken along the line 3--3 of Fig. 2.

Referring now to the drawings and particularly to Fig. 1, the numeral I generally designates a coaxial line oscillator including an electron discharge device 2 having a cathode 3, grid I and anode 5. The grid 3 is coupled by means of a disc 6 to the outer cylindrical conductor l of a coaxial line 8 whose inner cylindrical conductor 9 is hollow. Within the hollow inner conductor 9, a plurality of linear conductors I0, I I and I2 extend, and they are connected to the terminals I3, I4 and I5 of the cathode 3 of the electron discharge device 2. These linear conductors Ill-I2 supply the direct current potentials from a suitable source of power supply to said cathode. These direct `current leads carry heating current for heating the cathode, and the negative side of the B power supply. In order to keep the radio frequency current at the cathode terminals in the coaxial line 8 and to prevent it from entering the power supply, I provide a capacitive coupling assembly I6 or by-pass condenser arrangement, which serves to by-pass the radio frequency energy to the hollow inner conductor 9. A similar capacitive coupling assembly Il is also provided, assemblies I6 and I'I being arranged within the hollow inner conductor 9 towards opposite ends thereof, assembly I6 being adjacent the cathode terminals and assembly I'I being adjacent the outer end of the coaxial line 8.

In Figs. 2 and 3 the details of assembly I6 are illustrated. Since assembly Il is similar in construction the details thereof will be omitted. The assembly I6 includes a sheet I8 of dielectric material which is loosely wound around the inner surface of the hollow inner conductor 9. Abutting the inner surface of the wrapped sheet I8 of dielectric material are three conducting segments I9, 20 and 2l in the form of sectors of a circle, Aeach of said segments being separated or otherwise effectively insulated from the others and the segments are symmetrically disposed around the central longitudinal axis of the hollow cylindrical conductor 9. Each of said segments I9-2I has a tapering portion 22 extending longitudinally from the main portion 23 thereof. The segments I9-2I are spread apart and maintained in fixed position within the hollow inner conductor 9 by means of a tapered insulator `24 which slides within the tapered portions 22 of said segments and forces them outwardly. A screw 25, arranged in a central hanged collar 26 of insulating material between said segments and threadably engaging a iianged sleeve 21, extending through insulator 24 moves said insulator axially as said screw 25 is tightened thus bringing thicker portions of said insulator between the tapered portions 22 spreading said portions and the segments of which they are part, and forcing said segments against the dielectric material I8 which in turn is forced against the inner surface of the hollow inner conductor 9, thereby xing the assembly in place within said hollow conductor.

The linear conductors IIJ, II and I2 pass through openings in the segments I9, 20 and 2l respectively and are electrically connected thereto. While said linear conductors may be simply connected to their respective segments, for example by soldering 32, in assembly I6 other means are provided to enable these linear conductors to be conveniently connected with the terminals I3-I5 of the cathode of electron discharge device 2. For this purpose, a connector 28 is slipped over the end of each of the linear conductors ID, II and I2 and connected therewith, for example by pinching and soldering. Connectors 28 are soldered to their segments. A flexible cable 29 connects each connector 28 to a connector' 30 of the type having an opening therein for the reception of one of the terminals I3-I5 and having a screw 3l adapted to be turned to ysecure said terminal within the connector 30. By this arrangement, the entire assembly IS, including also the hollow inner conductor 9, may be inserted in the coaxial line structure I and connected to the cathode terminals by connectors 30.

In assembly Il, the linear conductors IB, I I and l I2 may be connected to the conductive segments thereof in any convenient manner as simply by soldering them within said segments.

It is preferred that the sheet I8 be substantially wider than the length of the segment as measured longitudinally in relation to the hollow inner conductor. Thus long leakage paths around the edges of the dielectric are provided.

While I have described the details of one embodiment of my invention, it will be apparent to those versed in the art that numerous changes may be made in these details without departing from the teachings thereof. For example, the dielectric might be applied in liquid form to the inner surface of the hollow inner conductor. Other changes such as in the means vfor connecting the linear conductors to the segments will occur to those versed in the art. vFurthermore it will be apparent that the number of segments may be changed depending upon the number of conductors which are to be coupled to thehollow inner conductor. Accordingly, while I have described above theprinciples of myfinvention in connection with specific apparatus, itis to be clearly understood that this description is made only by way of example and not as a limitation on the scope of my invention as defined in the accompanying claims.

I claim:

l. A capacitive coupling assembly for coupling one or more linear conductors, extending within a hollow conductor, to said hollow conductor, comprising one or more segmental conductive elements, one connected to each linear conductor, mounted within the hollow conductor about its axis, a dielectric member between said elements and the inner surface of the hollow conductor, and wedging means for radially expanding said segmental elements against the dielectric member to press the latter against the opposed inner surface of the hollow conductor.

2. A capacitive coupling assembly for coupling one or more linear conductors, extending within a .hollow conductor, to said hollow conductor, comprising a supporting member within said hollow conductor, conductive segments mounted on the support and each connected to one of said linear conductors, a dielectric member between said segments and the inner surface of said hollow conductor and wedging means between the support and said segments to spread the segments and press the dielectric against said inner surface.

3. A capacitive coupling assembly for coupling one or more linear conductors extending within a hollow elongated conductor to said conductor comprising an insulator within said hollow conductor having a Atapered portion extending longitudinally with respect to the hollow conductor, conductive segments mounted around and abutting said tapered portion and extending transversely of the hollow-conductor towards the inner surface thereof, each ,of said segments being connected to one of said linear conductors, a dielectric member between said segments and the innersurface of said hollow conductor, and wedging means for moving the insulator to advance thicker parts of the tapered portion thereof between said segments 'to spread the segments and press the dielectric against said inner surface.

4. A capacitive coupling assembly for coupling one or `more linear conductors extending within a hollow elongated cylindrical `conductor to said hollow conductor comprising an insulator arranged centrally within said hollow conductor and having a portion `thereof tapering axially, conductive members in the form of sectors arranged around and abuttingsaid tapered portion and extending radially ofthe central axis ofthe hollow conductor towards `theinner surface thereof, each of said sectors being lconnected to one of said linear conductors, a kdielectric member between said sectors and the inner surface of said 4hollow conductor, and means for moving the insulator axially to advance thicker parts of the tapered portion thereof between said sectors to spread the sectors and press the dielectric against said inner surface.

5. .Acapacitive coupling assembly according to claim 3 wherein each of said segments is spaced.

Aand `thereby insulated, from `each other.

6. A capacitivecoupling assembly according to claim 1 whereinsaid dielectric member consists of a continuoussheet of dielectric material loosely inserted in said hollow conductor contiguous to the inner surface thereof.

.7. A capacitivecoupling assembly according to claim v1 wherein saidfconductive segments have openings therein through which said linear conductors extend.

8. .Ina coaxial line device including `an electron dischargedevice having a plurality of electrodes; the .combination comprising a hollow inner conductor of said line connected'to one of said electrodes, a linear conductor connected to said electrodeand extending `within said hollow inner conductor, a dielectric member covering a portion of the inner suniace of said hollow conductor, a segmental conductive element connected to said linear conductor within the hollow conductor and adjacent said dielectric member, and wedging means for expanding said element against said dielectric member.

9. In a coaxial line device including an electron discharge device having an anode, cathode and grid, a coaxial line including an outer conductor coupled to the grid, and a hollow inner conductor the combination comprising, a plurality of linear conductors connected to the cathode terminals and extending within said hollow inner conductor, and means for capacitively coupling said linear conductors to said hollow conductor adjacent the cathode comprising an insulator within said hollow inner conductor having a longitudinally-extending tapered portion, conductive segments mounted around and abutting said tapered portion and extending radially of the central axis of the hollow conductor toward the inner surface thereof, each of said segments being connected to one of said linear conductors and having an opening therein through which said linear conductors extend. a dielectric member between said segments and the inner surface of said hollow conductor, and wedging means for moving the insulator to advance thicker parts of the tapered portion thereof between said segments to spread the segments and press the dielectric against said inner surface, thereby fixing the assembly within said hollow conductor.

EVERT M. OSTLUND.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 20 2,097,519 Gabriel et al Nov. 2, 1937 2,203,806 Wolf June 11, 1940 2,331,193 Hutcheson Oct. 5, 1943 

